In many applications, it is necessary to locate an object reliably with a high accuracy. For example, in an elevator system, the location of the elevator car must be measured within +/−10 cm between floors and within +/−1 cm at each floor. To achieve this accuracy, elevator systems employs a large number of location sensors in the form of switches. The installation and maintenance of switches is time consuming and costly. In addition, it is difficult to determine the location of the elevator car between floors, where there are no switches, in emergency situations.
FIG. 1A shows a conventional leaky coaxial cable 100. The cable includes a conductor 101, a separator 102, and a shield 103. Slits 104 transmit RF signals 105. Dual leaky coaxial cables have been used to detect intruders in surveillance systems. There, the moving object is passive, and the detection depends on a disturbance in the electromagnetic field between the cables, see U.S. Patent Application 2009-0153147, “Intrusion detection system.”